Blood in the Stool

Blood in the stool – either on opening your bowels or wiping afterwards – is ALWAYS abnormal. The commonest cause is haemorrhoids or “piles” but occasionally the cause can be more serious such as inflammation of the bowel or even bowel cancer.

Bowel cancer is the second most common cancer in men and women in the West. Although 1 in 20 people will develop bowel cancer, most bowel cancers are preventable be removing pre-cancerous polyps before they develop into a cancer. Bowel cancer screening is even more important if patients have a family history of bowel cancer as they may be at increased risk. Unfortunately, polyps generally don’t cause symptoms, so it is recommended that patients undergo bowel cancer screening testing even if they feel normal. Patients who have symptoms suggestive of bowel cancer such as rectal bleeding, change in bowel habit, abdominal pain or weight loss should be investigated promptly.

Bowel cancer (Colorectal cancer) develops from precancerous polyps in the large bowel (also known as the large intestine, colon and rectum). These grow slowly over five to ten years or more and some will develop into a bowel cancer. During this period they can be found by flexible sigmoidoscopy or colonoscopy and removed to stop cancer development. Other test for bowel cancer screening such as testing for blood in stool (faecal occult blood testing) mainly aim to detect early stage cancer before it is advanced.

Removal of precancerous polyps means that there is no chance of cancer spread; however, once a cancer develops there is risk of spread to other organs. Survival is much better for early stage cancers, stage I 95% survival at five years, compared to late stage cancers. Therefore, bowel cancer screening save lives, and prevents the need for surgery and chemotherapy or radiotherapy.

Methods for bowel cancer screening vary around the world. In the United Kingdom repeated testing for blood is stool is offered by the NHS to detect early cancers every two years. In the United States colonoscopy from age 50 is the preferred method, which permits detection and removal of precancerous polyps (cancer prevention) as well as early cancer detection, every 10 years.

Screening colonoscopy is safe, and the most effective method to prevent bowel cancer by removal of pre-cancerous polyps. If polyps are found more frequent colonoscopy may be indicated for surveillance. See the colonoscopy section for a more detailed description of the procedure.

STOP PRESS: American Cancer Society guideline says colorectal cancer screening should begin at age 45 for people at average risk.


Slow bleeding from the bowel can occur for a long time – many months or even years before it is noticed, and this can lead to anaemia.

Anaemia (low blood count, low haemoglobin) is commonly found by family doctors investigating patients for a range of symptoms including tiredness, lack of energy, pale skin or nails, shortness of breath, chest pains, and palpitations.

The most common cause for anaemia is low iron levels, as iron is required to make red blood cells. Iron is found in our diet in green leafy vegetables, meat eggs and fish. Loss of blood from somewhere in the gut (gullet, stomach, small bowel or large bowel) is the most common cause of iron deficiency anaemia.

Although anaemia lead to symptoms, it can be caused by other diseases such as stomach ulcers, coeliac disease (gluten intolerance), bowel inflammation (ulcerative colitis or Crohn’s disease), or cancers of the oesophagus (gullet), stomach or large bowel (colorectal cancer). Therefore, when iron deficiency anaemia is discovered it usually need prompt investigation. An exception is in younger women who can have anaemia due to menstrual blood loss.

Investigation of iron deficiency anaemia is directed towards finding the cause of blood loss. Current recommendations suggest gastroscopy and colonoscopy as first line investigations. Treatment involves management any underlying conditions found, but also iron replacement either with iron tablets, or more rarely with intravenous iron infusions. These usually rapidly correct the anaemia and improve symptoms and energy levels.


Colonoscopy involves gently passing a thin flexible video telescope through the anal canal and around the large bowel (colon) and sometimes into the last part of the small bowel (terminal ileum). Careful examination of these areas can reveal a range of gastrointestinal problems including inflammation (ulcerative colitis or Crohn’s disease), diverticulosis (pockets in the bowel lining), haemorrhoids (piles) or even bowel cancer. Biopsy samples (small pinches of bowel lining, a painless process) can be taken and sent to the pathologist to help confirm diagnosis.

If pre-cancerous polyps are found they can often be painlessly removed during the same colonoscopy (polypectomy) and this prevents them going on to develop into a bowel cancer. They are sent for analysis in the pathology laboratory. Removal of polyps is how bowel cancer screening by colonoscopy prevents bowel cancer.

Patients almost always elect to have sedation (an injection of medication to feel calm and sleepy) for the test to be more comfortable. After sedation you cannot drive and need someone to accompany you home. Less commonly patients have the test with “gas and air” (Entonox) which reduces but are fully awake for the test.

Colonoscopy is very safe, takes about 30 minutes and is carried out in the Endoscopy department, with risks and benefits discussed beforehand. Patients need to have medication to clear the bowel beforehand (Bowel prep), and this is arranged in out patients. Patients are usually ready to leave the department approximately an hour after their test and can return to normal eating the same day, and normal activities the following day.

Case Study

John Smith (not his real name) had noticed intermittent blood when he went for a bowel movement for more than a month. Sometime this was bright red on the paper, sometimes mixed in with the stool. He was 55 years old and was worried by this, and thinking about it a lot, so went to see his GP. His GP examined him and though this might be related to haemorrhoids (Piles), but given he was over 50 he felt that a colonoscopy was needed to make sure there was not any other cause further up the bowel.

John came to see me for a discussion about colonoscopy. We discussed that colonoscopy was the best test to make sure that there was nothing more serious in the bowel, and that is was safe, quick and comfortable, and that we would give him sedation to make sure he felt relaxed.

A week or so later we performed the colonoscopy, which took less than 30 minutes and we found and removed a small 1cm benign pre-cancerous polyp (Adenoma) that might have been the cause of the bleeding. There were no other worrying diagnoses. John was reassured and wondered why he didn’t seek advice sooner.

Having found a pre-cancerous polyp, it has been stopped in the process of turning into a cancer by being removed, reducing future bowel cancer risk; however John was reassured that he will have a further surveillance colonoscopy in a few years time to make sure no further polyps have developed.

FIT Bowel Cancer Screening programme video

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